1. Field of the Invention
The present invention relates to a purifying apparatus for flowing water. In more detail, the invention relates to a purifying apparatus that operates by oxidation and decomposition of water pollution substances in a river, which is effective for use such as elimination of nitrogen and phosphorous which are substances that cause eutrophication of the flowing river water.
2. Description of the Related Art
Hitherto, in regard to a purification of the water pollution substances in the river, although a contact oxidation method by a biological membrane having a membrane in which microbes living in the river naturally grow has been developed and applied, this method is suitable mainly to purify carbon sources contained in waste water, but it is not suitable to eliminate nitrogen and phosphorous which are substances that cause eutrophication.
Therefore, in the prior art, in order to prevent the eutrophication it has been necessary to decompose and eliminate nitrogen and phosphorous other than the carbon sources, so that the biological membrane treatment method is not necessarily sufficient. Further, there have been studied countermeasures such as a nitrification/denitrification by a nutrient salt inclusive fixing method in which the biological membrane has been strengthened and about application of an ammonia phosphate crystallizing method using Mg salt, but they have such serious shortcomings that an elimination rate of nitrogen cannot exceed 60% in a case where the ammonia in the river is eliminated, that a sufficient elimination rate cannot be ensured depending on a C/N ratio, and that even if dissolved oxygen is sufficiently ensured in the river flow the nitrification does not proceed because a reaction velocity of nitrifying bacteria is low for the nitrification of ammonia for a nitrogen. Accordingly,means for increasing the elimination rate of nitrogen and phosphorous to 90% or higher has become necessary at any cost.
Therefore, an object of the invention is to provide a now purifying apparatus capable of effectively eliminating the water pollution substances such as nitrogen and phosphorous in the flowing water in the river and the like, thereby solving the problems mentioned above of the prior art.
As one means for achieving the above object the invention provides a purifying apparatus for flowing water in which a negative electrode plate is disposed on a flowing water bed and a positive electrode plate is disposed in an upper face opposite to the negative electrode plate, characterized in that the positive electrode plate is adapted so as to be dipped below a water surface of the flowing water with floats being disposed at least at the front/back (i.e. upstream/downstream ends) or left/right (i.e. opposing sides) of the positive electrode plate in a flowing direction of the flowing water, in the positive electrode plate there is arranged means for disposing it to an opposed upper face position with respect to the negative electrode plate, and the positive electrode plate and the negative electrode plate are provided with an electric field generator so that water pollution substances contained in the flowing water are oxidized and decomposed by a generation of high electric field pulses.
The invention intends to solve the problems by means of generating O-radical (oxygen radical) and OH-radical (hydroxy radical), which are generated by the high electric field pulses and have a high oxidizing power, on a metal face for nanosecond to microsecond, oxidizing mainly a carbon source and a nitrogen source in a polluted water, which impinge against these radicals, and cohering phosphorous by a cohesive reaction of particles in accompaniment with an electrification of H+ ions generated on this occasion to floating suspended substances so as to deposit as sediment and separate the phosphorous, thereby achieving by one pass operation an elimination of the pollution substances at 90-95% which could not be attained by the prior art.
And, in a concrete implementation mode, since a water level and a flow rate of the flowing water change together with a structure of the purifying apparatus, in order to cope with this, the fact is taken into consideration that it is necessary to automatically control a supplied watt-hour by the flow rate of the water and a concentration of SS such that it becomes a suitable optimum watt-hour to thereby maintain the elimination rate of the pollution substances constant. For example, since the flowing water in a river greatly changes depending on time during one day and a ratio between when the flow rate is minimum and when it is maximum reaches 1:10-20, it follows that a magnitude of the flow rate is proportional to a passing velocity, so that, in order to supply an electric power tracing the magnitude of the flow rate, it is necessary to adjunctively provide a control unit for adjusting the supplied watt-hour which is optimum and minimum with respect to the flow rate, the floating suspended substances and a water depth. Further, in an emergency time such as a flood, the present apparatus must be provided for being shunted so as not to become an obstacle in the flowing water.
Therefore, first, in a structure of the purifying apparatus of the invention, the following modes are taken into consideration as being suitable ones, although not limited to these.
 less than 1 greater than  In the positive electrode plate, there is provided means for vertically moving it.
 less than 2 greater than  Gas collecting means (for collecting a gas generated by oxidation and decomposition) is provided.
 less than 3 greater than  The positive electrode plate has at least one positive electrode substance among metals (including alloys; hereafter, ditto) and metal oxides.
 less than 4 greater than  The positive electrode plate is composed, for example, of a base plate which is metal, ceramics or resin or a composite body of more than two of the formers, and of the positive electrode substance.
 less than 5 greater than  The positive electrode substance is at least one of, for example, titanium oxide, ruthenium oxide, cobalt oxide, nickel oxide, tin oxide and platinum.
 less than 6 greater than  In a more concrete example, in the positive electrode plate, at least one of titanium oxide, ruthenium oxide, cobalt oxide, nickel oxide, tin oxide and platinum is integrated with a plate of porous titanium, porous ceramics or stainless.
 less than 7 greater than  The positive electrode plate is adapted such that its dipped depth from a water surface is ⅕-{fraction (1/10)} of a water depth.
In the invention adapted such that the water pollution substances contained in the flowing water are oxidized and decomposed by the generation of high electric field pulses, how the positive electrode plate should be constituted is practically a very important point in order to make the generation of high electric field pulses and actions of the aforesaid radicals by the generation effective ones. More suitably, in the invention, as the positive electrode substance, the metal oxide or a noble metal is used. Such a metal oxide called titanium oxide, ruthenium oxide, cobalt oxide, nickel oxide or tin oxide, or platinum as mentioned above is effective.
As to the positive electrode substance, in a case where it is the metal oxide, it maybe one formed by making its particles into a green compact and baking or sintering it, or one in which the substance or its particles is/are born on a suitable base plate. As the base plate for bearing on this occasion, it may be, for example, a plate of porous titanium, porous ceramics or stainless etc., which has a high corrosion resistance, and it is preferable that the positive electrode substance constitutes a positive electrode face portion in a membrane-like form. The base plate itself way be made conductive, or the positive electrode substance in the membrane-like form may be caused to have a conductive property.
The metal oxide may be integrated with the base plate by an adhesion-integration by deposition, distillation and the like, or means such as application of a gel solution.
In case of platinum, a surface plating may be adopted, or a platinum foil may be adhered.
Incidentally, as to a negative electrode, various substances may be adopted so long as they are metals having a high corrosion resistance or ones whose surfaces are coated with the metals. For example, a stainless plate and a metal plate coated with the platinum foil are exemplified.
It is practical that the positive electrode is adapted to be dipped from the water surface by vertically moving means and, further, it is desirable that the positive electrode plate is provided in its vicinity with gas collecting means.
Further, it is preferable in the invention that the positive electrode plate has a concave curved face opposite to the negative electrode in viewpoints of generating the high electric field pulses and collecting a decomposed gas.
Concretely exemplifying and explaining, for example, in the purification apparatus by oxidation and decomposition of the invention, the stainless plate or the metal plate coated with the platinum foil is made the negative electrode; titanium oxide, ruthenium oxide, cobalt oxide, nickel oxide, tin oxide or the platinum foil is adhered to an upper face of die-cast plate etc. of conductive porous titanium or stainless parallel in face to the metal plate; one in which the aforesaid upper face is slightly curved in a concave state relative to the negative electrode is made the positive electrode plate; floats are attached to the positive electrode plate at its front and back; there is provided a structure in which the positive electrode plate is dipped to ⅕-{fraction (1/10)} of a water depth; and there is provided a structure in which the floats are vertically movable at four corners of the positive electrode plate. Further,a sealant is applied in order to prevent a gas generated by the decomposition form escaping, and a gas reservoir is provided, thereby making it possible to collect the generated gas.
And, it is preferable that the purifying apparatus of the invention is adapted such that the water flow impinges against an oxidizing electrode face (positive electrode plate) under a turbulent flow state by high electrode field-pulse waves, and an oxidizing reaction of pollution substances continues for at least 2-3 seconds. Further, as mentioned above, it is desirable to prevent the gas generated by oxidation and decomposition from being discharged into the air. Since the oxidizing reaction occurs by a physicochemical reaction, N2 and NOx are generated in regard to N source, noxious gasses of SOx and H2S are generated in regard to S source, and CO2 gas is mostly generated and CO gas is slightly generated in regard to C source. It is desirable that these intermediate products are reduction-treated by hydrogen and the like. Treating means and a treating unit therefor are also proposed in the invention.